1. Field of the Invention
The present invention relates to a refrigerator, and, more particularly, to a refrigerator having a step motor valve to control the supply of a refrigerant to a plurality of storage compartments.
2. Description of the Related Art
A refrigerator is a device to maintain the freshness of various foods for a long time. For this, the refrigerator produces cold air via a refrigeration cycle, and supplies the cold air into a storage compartment thereof. Generally, the refrigerator includes a compressor, a condenser, an expansion valve, and an evaporator, so that it cools the storage compartment by use of heat transfer based on the phase variation of a refrigerant.
Some refrigerators include a plurality of storage compartments. A refrigerant cycle of these refrigerators is controlled so that foods having different storage temperatures are separately stored in the plurality of storage compartments. For the control of the refrigerant cycle, a refrigerant pipe, forming the refrigerant cycle, is provided with a refrigerant control valve to control the flow of a refrigerant.
Conventional refrigerators having a plurality of storage compartments mainly use a 3-way valve as the refrigerant control valve. For example, when a refrigerator has two storage compartments, the 3-way valve, which has a single inlet and two outlets, is able to distribute a refrigerant to the respective storage compartments. Recently, refrigerators having three or more storage compartments have been mass-produced. In this kind of refrigerators, two 3-way valves or a single 4-way valve having a single inlet and three outlets are used to control the flow of a refrigerant.
However, the use of two 3-way valves has a problem in that the two 3-way valves require a relatively large installation space, causing an increase in the overall size of the refrigerator. This also increases manufacturing costs, resulting in a high product price. Furthermore, as compared to using a single valve, using two 3-way valves requires a complicated control method due to numerous opening/closing combinations.
On the other hand, a 4-way valve suffers from a complicated interior structure thereof although it solves the above problems to some extent. Among three outlets of the 4-way valve, one outlet is adapted to be opened or closed by use of an opening/closing member, which is different from ones adapted to open or close the remaining two outlets. This has a necessity of a complicated algorithm to control the respective outlets.
Moreover, the conventional refrigerators using two 3-way valves or a single 4-way valve as stated above have a problem in that they cannot accurately control temperatures of the respective storage compartments when all outlets of the valve(s) are simultaneously opened to refrigerate the plurality of storage compartments. More specifically, even if all outlets of the valve(s) are simultaneously opened, a refrigerant cannot be equally distributed via the respective outlets for several reasons, for example, due to a difference in the resistance of refrigerant pipes extending to the respective storage compartments. Thus, the unequal amount of a refrigerant is supplied to the respective storage compartments, making it impossible for a system, which determines the supply amount of a refrigerant based on the opening time of a valve, to accurately measure the amount of the supplied refrigerant. This consequently disables accurate control in the temperature of the respective storage compartments.